Anaesthetic agents are administered routinely based on predetermined dose requirement which is according to patients' age and body weight. MAC (Minimum Alveolar concentrations) of anaesthetic agents as well as plasma drug concentrations required for producing anaesthetic state vary in different individuals depending upon the altered drug pharmacokinetic (what body does to the chug) as well as dynamics (what drug does to body) due to different disease states (pathological states) of patient population visiting for anaesthesia and surgery. Even among normal healthy individuals, there are variations in pharmacokinetic (drug disposition by body) and pharmacodynamic (drug effect on body) of anaesthetic drugs used in clinical scenarios. Consequently administration of anaesthetic drugs is titrated using hypertension and tachycardia (alteration in haemodynamics) as indicators of inadequate depth of anaesthesia. However, the disadvantage associated with the same is that, blood pressure and heart rate are not reliable indicators of depth of anaesthesia as a large number of cardiovascular drugs like β-blockers and other anti-hypertensive may affect the blood pressure and heart rate. In view of this, there is need to monitor objectively the drug effect or depth of anaesthesia. EEG has been used to indicate the depth of anaesthesia, but the ideal control variable for the delivery of anaesthetics is still unknown1. Various electrophysiological (EEG) variables have been used in an attempt to provide measure of anaesthetic depth2 though the success is limited2-4. Simple measures of EEG like spectral edge frequency (SEF), Median edge frequency (MEF) correlate poorly with clinical parameters of depth of anaesthesia. The Bispectral index (BIS) is a derived variable of the EEG that provides a measure of the consistency of phase and power relationships among the various frequencies of the EEG5. The BIS describes the complex EEG pattern as a single variable which has been used for control of anaesthesia and approved by FDA for anesthetic depth monitoring.
Attempts have been made in the West to control anaesthetic agent's delivery using closed loop drug delivery4,5. Various parameters such as median frequency of EEG or auditory evoked potentials have been applied as controlled variable for closed loop control of hypnotic anesthetic drugs in the literature.
All these attempts have used Target Controlled infusion pumps for titrating the drug delivery to different indicators of depth of anaesthesia. In spite of that, no closed loop anaesthesia system is available commercially. Target controlled infusion pumps are not only 3-4 times constlier than the simple syringe pump but they also require special prefilled syringes of drug for controlling the delivery of Propofol.
None of the systems developed so far incorporate both intravenous as well as inhalational anaesthetic agents together. None of the system provides versatility to the anaesthetist or user to change from one type of anaesthesia i.e. intravenous anaesthesia to other type of anaesthesia i.e. inhalational anaesthesia and vice versa. None of the system suggested earlier incorporate safety features regarding the effect of anaesthetic agent on blood pressure and heart rate and controlling anaesthetic delivery governed by these factors.
Normally the drug is administered and the monitoring equipment monitors the effect. The clinician reads the display of the monitor and then changes are made in the drug delivery system to alter the rate of delivery of the drug. The process is repeated after observing the changes in the monitored value, which may cause the following:                Time delay in display of the monitored value,        Time delay in reading the value,        Time delay in comprehending the change in monitored value,        Time delay in altering manually the drug delivery,        Human error in reading, judging and altering the drug dosage.        
Further, reference may be made to “A new closed-loop control system for isoflurane using Bispectral index wherein Automatic control of depth of hypnosis using the BispectralIndex (BIS) can help to reduce phases of inadequate control.
Yet further, reference may be made to “Titration of propofol for Anesthetic induction and maintenance guided by the Bispectral index. This report describes a closed-loop titration of propofol target control infusion based on a proportional-differential algorithm guided by the Bispectral Index (BIS) allowing induction and maintenance of general anesthesia and compares this to manual propofol target control infusion.